To reduce noise emission into the environment by a gas-carrying line in which the gas flow also carries airborne sound, it is conventional to use a muffler of the type defined above in such a line. The gas transported in the line flows through the muffler. At the same time, the airborne sound entrained with the gas enters the muffler and is dampened there, e.g., by reflection, resonance and sound absorbent materials. The gas then flows out of the muffler at a reduced airborne sound level. Such mufflers are preferably used in the exhaust systems of internal combustion engines, in particular in motor vehicles, to dampen the sound generated by the internal combustion engine, propagating through the exhaust system. Likewise it is fundamentally possible to provide a muffler in the fresh air system of an internal combustion engine to dampen the sound generated by a compressor for an exhaust gas turbocharger, for example. However, the suppression of airborne sound may also be of interest with other lines that carry gas, so the present invention should not essentially be limited to applications in internal combustion engines.
Thermal expansion effects will necessarily occur if the line in which the sound propagation that is to be suppressed is carrying hot gases, as is the case with the exhaust system of an internal combustion engine, for example. To prevent the resulting damage to the muffler, it is customary in the case of inside pipes that carry gases and run in the interior of a housing of the muffler to insert one pipe inside the other so that they have axial mobility in relation to one another and thereby create a sliding seat. Thermally induced expansion effects can be compensated thereby in such a sliding seat because the two inside pipes are axially movable in relation to one another in this sliding seat. In addition, it is conventional to reinforce the housing of such a muffler by providing at least one inside plate. Depending on the gas guidance in the interior of the muffler, the inside pipes must be passed through such an inside plate. At the same time, such inside plates are utilized to secure the inside pipes in the housing. It is conventional here to mount one inside pipe on a first inside floor in proximity to the sliding seat and to mount the other inside pipe on a second inside floor, which is spaced a distance away from the first inside plate. The two inside plates are arranged on both sides of the sliding seat. To stabilize the inside pipes as effectively as possible in the housing, it is expedient to support the two inside pipes over the two inside plates as close to the sliding seat as possible. Since the two inside plates are therefore only a comparatively small distance away from one another, the housing has a particularly high rigidity in this area. However, the introduction of such an inside plate is associated with a comparatively high cost, at least in mass production. Furthermore, this increases the weight of the muffler.